Paper making machine



-P 1940- s. P. H. E. HOLGERS4SON 2,198,387

PAPER MAKING MACHINE Filed April 27, 1937 Patented Apr. 23, 1940 PATENT OFFICE PAPER MAKING MACHINE Sigbjiirn Paul Herbert-Ebbinghaus Holgersson,

Hammarby, Storvik, Sweden Application April 27, 1937, Serial No. 139302 In Sweden April 26, 1935 2 Claims.

With a view to increasing the productive capacity of or decreasing the consumption of heat by drying-machines for paper, boards or pulp, it has been suggested that the pulp-web should be subjected to the direct action of steam before the former passes through the presses. The methods hitherto known for the application of this idea have, however, not given satisfactory results. This fact is probably due to the circumstance that sufficient attention has not been paid to the factors which are of importance in this connection.

' The experiments on which the, present invention is based have shown, that, to achieve a better result, it is of the greatest importance that the steam is applied to the pulp-web in aparticular manner at the most suitable point and that the uncondensed steam is utilized for pre-heating Cir the pulp-web.

The characteristic feature of the invention is, that steam is applied to the paper or pulp-web at or immediately before the place where the pressure of the press is applied and that uncondensed steam is caused to flow from that place along the surface of the pulp-web, in the opposite direction to the movement of the latter, for the purpose of pre-heating it. The steam may first be introduced through nozzles into a chamber-a so-called steam-box-where it can recover the heat it loses on issuing from the nozzle or nozzles as a result of the high kinetic energy, before being applied to the paper or pulp-web through an opening at the front end of the steam-box, as close as possible to the place of pressure.

It is also of importance that the steam is applied to the paper or pulp-web in such a manner that the condensed water formed on or near the surface of the pulp is pressed into the pulp when the web passes through the press and forces colder water out through the opposite side of the pulp-web. The steam should be applied to the pulp from the side opposite to the felt.

By this method, good heat-economy is achieved and it is possible to use very high pulp-temperatures without, in the case of felt-presses, risking overheating either of the felts or of the rubber on the press-rolls.

The invention also includes a device for the application of the above method.

The annexed drawing shows some examples of devices for the practical application of the invention. Fig. 1 is a schematic sketch, showing a pulp-preheater on an ordinary felt-press, Fig. 2 shows a pulp-preheater on a high-pressure press. Fig. 3 shows a section along the line A-A in Fig. 2.

l and 2 represent the press-rolls, of which the upper one, I, may be a steel roll while the lower one, 2, may suitably be jacketed with rubber. The felt, which is represented by dotted lines in Figs. 1 and 2, is indicated by 3 and ,the pulp partments. The distance between the branch,

pipes may suitably be 250-350 mm. Along one end of the steam-box there is a slit D through which the steam is blown on to the pulp-web. The steam-box is so placed that the slit D is at as short a distance as possible from the line of contact betwen the pulp-web and the upper press-roll. E is a space between the bottom of the steam-box and the surface of the pulp-web which forms the so-called pre-heating chamber. On both sides of the pulp-web, before the latter has passed the guide-roll C, which is journalled in the gable-plates of the preheater, there are plates or hoods K, the bottom ends of which are formed into gutters L. By M is designated a packing-plate which can be adjusted with reference to the roll I and having for its object to prevent the steam from flowing upwards. These hoods and the guide-roll should be so placed that the dropping of condensed water on the pulpweb is prevented.

The device functions in the following manner:

The steam conveyed from the main pipe A by the branch pipes-B to the steam-box C is blown through the slit D on to the pulp-web and inpinges on' it at the shortest possible distance from the line of contact between the pulp-web and the upper press-roll I. The steam which is not immediately condensed between theslit D and the said line of contact passes through the second preheating chamber E and there preheats the surface of the pulp-web.

The steam issuing from this preheating chamber passes into the preheating chamber F where it brings about a first preheating of the pulp and any condensed water which may be formed on the plates K runs down into. the gutters L, 'from which it is led away.

The hoods K are hung up in such a manner that they can be removed when starting-up. As it is possible to limit the quantity of steam so that it is completely condensed in the chamber E, the hoods K may then be dispensed with.

The device shown in Fig. 2 is the same as in Fig. 1. except that the hoods K are removed. It will be seen that the steam-box is inclined upwards towards the slit D, which is an advantage since the uncondensed steam which flows downwards through the chamber E is forced to remain in that chamber and does not seek to escape through leaks. Suchleaks of steam usually involve the entrance of air, which prevents the condensation of steam on the pulp-web.

As has been indicated above, it is important that the supply of steam takes place in such a manner that the temperature vof the steam when it impinges on the pulp-web close to the point of pressure is sufliciently high. Such a high temperature is made possible by applying the steam in the manner described above, i. e. so that after it leaves the branch-pipe B, it is enabled in the steam-box to convert its kinetic energy into increased heat-contents before it impinges on the pulp-web. If on the other hand, the steam is sprayed direct from the steam-pipe on to the pulp-web, as has hitherto been the case, the temperature of the steam falls when it leaves the nozzle owing to the high velocity which is then unavoidable. When the steam is first led into a steam-box according to the present invention, it has only a low velocity when it, meets the pulp-web. and, in consequence, high heat-contents. By suitably adjusting the flow-area of the branch-pipes B, it is possible to attain uniform heating across the whole width of the pulpdevices according to the present invention are employed, the pulp-web, when it leaves the pressroll I and is passed on to the drying cylinders,

. has a very high temperature, for example SO-85 C. This temperature is, in fact, higher than or, at least, as high as at any point on the drying cylinders. Since, however, the press-rolls acquire practically, the same temperature as the pulp-web, care must be taken that the temperature of the steam is not so high that the rolljournals are damaged or, alternatively, the latter should be provided with suitable cooling devices.

According to the present invention, the abovementioned advantages regarding increased production and reduced steam-consumption are due to the following causes: The capacity of the presses for pressing-out water is considerably increased when the temperature of the pulp-web is raised.

Thus, the contents of dry pulp in the web are considerably higher when using a steambox according to the present invention then without such a box, which relieves the dryingsection and thus makes it possible to increase the production.

According to this method, the temperature of .the pulp-web when it leaves the press is suitable for effective drying. When a steam-box is not used the temperatureof the pulp-web is low-' er (usually 20-50" 0.), and, as effective drying does not commence until a temperature of IO- C. is reached, the pulp has to pass through a portion of the drying section before reaching this temperature, which means that that portion of the drying section serves only as a preheater.

The increase per cent in the total steam consumption per unit of time of the machine, resulting from the use of a steam-box, is considerably lower than the increase per cent in the production of the machine. In this manner, in spite of 'the above-mentioned increase in the consumption of steam per unit of time, the consumption per ton of paper, boards or pulp produced is lower.

The present invention gives, however, another advantage in addition to those mentioned above, iz., when working with pulp which is rich in resin. Hitherto, the difficulty has arisen that resin is deposited on the upper press-roll so that it has been necessary to wash the latter frequently with petroleum or other solvent. The high temperature attained according to the present invention removes that difliculty since, at such high temperatures, the resin does not adhere to the roll.

Another advantage is that the pulp-web is washed with distilled water when the condensed water is pressed into the web and forces out the more or less dirty water previously there.

It is obvious that the details shown and described may be varied in many ways without departing from the scope of the invention.

I claim:

1. In a machine for drying a pulp-web, the combination of a press, consisting of two cooperating press-rollers, and a steam box having a slot-shaped outlet at the front end, said front end and outlet being located in close proximity to the place of pressure of the press, means for introducing steam into said steam-box, the bottom of the steam-box being substantially Darallel to and located at such a. distance from the surface of the pulp-web that a passage is formed between them through which the uncondensed steam flows in the opposite direction to the movement of the web for pre-heating the latter, and end hoods located at a distance from the web and in front of the steam box in the direction of movement of the web, so as to form a continued passage for the steam not condensed after having passed through the intermediate space between the web and the bottom of the steam box.

2. In machines for drying a pulp web, the combination of a press. consisting of two cooperating press-rollers, and a steam box having a slotshaped outlet at the front end, said front end and outlet being located in close proximity to the place of pressure of the press, the bottom of the steam box being substantially parallel to and located at such a distance from the surface of the pulp web that a passage is formed between them through which the uncondensed steam flows in the opposite direction to the movement of the web in order to preheat the same, vertical partitions in said steam-box dividing the same into a number of compartments extending inthe longitudinal direction of the web, valve controlled conduits for introducing steam into each of said compartments from a steam pipe, end hoods located at a distance from the web and in front of the steam box in the direction of movement of the web, so as to form a passage for the steam not-condensed after having passed through the intermediate space between the bottom of the steam box and the web, and gutters at the lower endsof said hoods for leading away the water of condensation.

srGBJoRN PAUL HERBERT EBBINGHAUS HoLGEassoN. 

